1. Field of the Invention
The present invention relates to a broadcast reception device capable of having a smart antenna connected thereto, and specifically to those adapted to detect whether or not the antenna is connected thereto.
2. Description of the Related Art
There is known a smart antenna capable of switching the direction of the directivity to receive airwaves transmitted from different directions. Smart antennas control a plurality of antenna elements to adjust receiving sensitivity in every direction. Therefore, the smart antennas are different from uni-directional antenna having fixed directivity in channel search method. Here, the channel search denotes a process of tuning channels the antenna can receive. Therefore, in the receiver to which the smart antenna and the uni-directional antenna can selectively be connected, the user is made to discriminate the antenna connected thereto, and the channel search is automatically processed on the receiver side based on the discrimination result.
As an example thereof, by displaying a menu panel for selecting the type of the antenna on a screen and the user designating the type of the antenna on the menu panel, the receiver selects a setting method of the channel. Such a channel search method based on the designation by the user requires the user performing the operation to recognize the type of the antenna connected thereto.
As a method of automatically setting the channel search, there is disclosed a technology for switching the channel search corresponding to the antenna connected there to, utilizing the receiving strength varied in response to the smart antenna switching the direction of the directivity (see, e.g., JP-A-2006-25199 (Patent Document 1) and JP-A-2006-157338 (Patent Document 2)).
Further, although the channel search is not performed automatically, there is disclosed a technology of discriminating the type of an antenna connected to in-vehicle equipment based on the value of a voltage applied to an antenna resistance (see, e.g., JP-A-2006-186967 (Patent Document 3)).
Further, although the channel search is not performed automatically, there is disclosed a technology of discriminating the type of an antenna connected to in-vehicle equipment by monitoring a current flowing in an amplifier of the in-vehicle equipment (see, e.g., JP-A-2005-354253 (Patent Document 4)).
Further, there is disclosed a technology of switching the antenna with which a television broadcast signal is received by operating an antenna changing-over switch for switching the connection of different antennas when receiving the television broadcasting (see, e.g., JP-A-2006-157340 (Patent Document 5)).
The technologies according to the Patent Documents 1 and 2 described above have the following problems. That is, the method of discriminating whether or not the smart antenna is connected based on the receiving strength causes the necessity of driving the smart antenna once for detecting the receiving strength in every direction. Therefore, in the case in which the uni-directional antenna is connected, the channel search process in the smart antenna described above has no meaning, and the time taken by this process becomes a waste.
Further, since the technologies according to the Patent Documents 3 and 4 are not the technologies for automatically performing the channel search, it is hard to apply them to the present case.
Further, the technology according to the Patent Document 5 is for performing switching by making the user operate the antenna changing-over switch, but not for performing the channel search automatically.